The invention relates to a plate heat exchanger comprising flow channels through which a first and a second flow flows in concurrent or countercurrent flow, which flow channels are formed for the first medium between individual plates joined together to form in each case a pair of plates, and for the second medium between pairs of plates joined together to form a stack of plates, wherein the individual plates and the pairs of plates are connected to each other at longitudinal edges and support surfaces running parallel to the main flow direction, wherein each individual plate comprises inflow and outflow cross-sections arranged diagonally and corresponding in the longitudinal direction for the first medium, and inflow and outflow cross-sections adjacent thereto in the transverse direction for the second medium, wherein the outflow cross-sections for the first medium are in each case offset by half the height of the inflow and/or outflow cross-sections for the second medium, wherein the individual plate is provided with a profiling that generates turbulences.
Plate heat exchangers of this kind are used on a large scale with plate dimensions of several meters. A field of application here is the use in incinerators, power plants, chemical plants, refineries and/or the like, in which the resulting combustion heat of the flue gas is used for heating the second medium.
A plate heat exchanger according to the aforementioned type is disclosed in detail in German patent DE 41 42 177 C2. Here, for increasing the efficiency of the heat exchanger or, alternatively, for reducing the dimensions of the required individual plates, guide blades are provided which distribute the medium flowing in through the inflow cross-section over the full channel width of the flow channel. In order to avoid dead zones in the inlet region, in particular in the plate region located mirror-symmetrically adjacent to the longitudinal center, the guide blades are provided with elongated outflow legs which protrude beyond the longitudinal center of the individual plate. In addition, for equalizing the flow within the flow channel, the guide blades are arranged closer to the inflow cross-section in the longitudinal center of the individual plates than in the direction of the longitudinal edge of the individual plate. The turbulence-generating profiling, which covers a surface area of the individual plates that is as large as possible, serves for the same purpose.
Although this arrangement has proved itself in practice, there are still problems due to flow bypasses which form on the individual plate and which allow the heat medium to flow interaction-free along the profiling. This relates in particular to the edge regions of the individual plate. As a result of this, the heat flow rate of the plate heat exchanger decreases so that said heat exchanger needs correspondingly longer individual plates for a required performance.
It is therefore an object of the invention to provide a plate heat exchanger with which the interaction-free flow of heat medium through the individual plate is as low as possible, and therefore the heat flow rate at constant plate dimension increases.